Volatile liquids, such as gasoline or other fuels, are generally delivered to the fuel tank of an automobile or other vehicle using a fuel dispensing nozzle. During delivery, gasoline vapors may evaporate from liquid gasoline due to heat and/or agitation of the gasoline. If these vapors are not recovered, they may escape from the nozzle, contributing to air pollution and/or wasting fuel resources. Thus, recovery of vapors resulting from the delivery of gasoline may be desirable and, in addition, may be mandated by regulatory agencies. For example, in the 1970's, the State of California enacted legislation requiring recovery of at least 94.5 percent of all vapors resulting from fuel delivery.
To recover gasoline vapors during delivery, fuel dispensing nozzles having a coaxial construction are often used. The nozzle generally has an inner spout connected to a supply line which provides a supply outlet for the gasoline being supplied to the fuel tank being filled. A vapor conduit, such as a boot assembly, surrounds the inner spout which has a vapor inlet proximate the supply outlet. The nozzle is connected to a coaxial hose, which is connected to a valve which separates the supply line from the vapor line.
Generally, the nozzles and hoses are connected to stationary pumps, such as at service stations, which are connected to storage tanks, often located underground, that store large volumes of fuel. Vapor recovery systems for such stationary fuels sources have been proposed and implemented which recover a substantial amount of the vapors from fuel dispensing nozzles. For example, U.S. Pat. No. 4,068,687 issued to Long discloses a system which includes a hydraulic motor and a pneumatic pump synchronized with one another and connected to the supply and vapor lines, respectively. The gasoline flowing from the supply pump drives the hydraulic motor, and the pneumatic pump then withdraws vapors from the fuel tank being filled, which may then be directed back to the storage tank. Similarly, U.S. Pat. No. 5,207,249 issued to Healy discloses a liquid jet gas pump that may be mounted in the main supply line to create a vacuum in a vapor line.
For mobile fuelers, such as fleet fueling trucks, however, conventional vapor recovery systems have been unable to efficiently recover gasoline vapors during delivery. Vapor pressures encountered in the storage tanks of mobile delivery systems may be substantially higher than those found in underground stationary tanks, for example, due to increased heat experienced by mobile fuel truck storage tanks and/or increased agitation of the gasoline resulting from movement of the fuel truck. Despite regulations in California and elsewhere since the 1970's, an efficient vapor recovery system for mobile fuelers has not been successfully developed.
Accordingly, there is a need for a more efficient vapor recovery system for mobile fuelers.